When drilling an oil or gas well the normal procedure is to drill a large diameter borehole for a relatively short depth of not more than a maximum of several hundred feet. A length of relatively large diameter surface pipe is positioned in this vertical hole and cement is forced into the pipe to flow upwardly in the annular area exterior of the pipe to anchor it solidly in the earth. Thereafter, the borehole is drilled down through the surface pipe to a total depth sufficient to penetrate a producing formation which typically is more than a thousand feet and can extend up to more than two miles in total depth. To produce a well it is necessary to install casing and sometimes, in addition to casing, tubing within the well, the casing and tubing extending the full depth of the borehole from the earth's surface down to the producing formation. Tubing and casing in a borehole must be supported. That is, tubing and casing must be secured at it's upper end to hang within the borehole. Neither tubing or casing are ever inserted in a borehole and allowed to rest on their lower ends. For this reason, it has historically been a practice by those who are expert in drilling and completing oil and gas wells to hang or suspend tubing and casing strings within a borehole. More particularly, the standard practice is to hang or suspend casing and tubing strings from well head equipment fixed to the upper end of a surface pipe that has been anchored in the earth.
Accordingly, sophisticated well head equipment has been devised over the years of the petroleum industry for suspending casing or tubing within a borehole. In recent years, increased emphasis has been placed upon sophisticated drilling and production procedures that sometimes require suspending more than a single string of casing or a single string of tubing in a well borehole. As an example, in some drilling procedures it is highly desirable that an ancillary, usually reduced diameter string of tubing be run exterior of an and parallel with a casing string. The ancillary tubing string can typically be of much smaller diameter than the casing.
A technique which has been developed of running the smaller diameter tubing in a borehole that is in a coil. Whereas casing and tubing are typically run into a well by threading end to end straight lengths of casing or tubing when a relatively small diameter supplementary tubing is required it can be in the form of a long length of tubing that is coiled and that is uncoiled as the small diameter tubing is inserted into a well and, when removed from the well, is received and stored in the form of a coil.
The utilization of one or more supplementary small diameter tubing strings in conjunction with a centrally supported casing has introduced new and sophisticated requirements to well head systems. The invention disclosed here is an improved casing and coil tubing hanger system that facilitates the installation of one or more small diameter strings of tubing in conjunction with a centrally positioned casing suspended from a wellhead.
For background information on tubing hanging methods and apparatus reference may be had to the following previously issued United States Patents which are by reference.
______________________________________ U.S Pat. No. INVENTOR TITLE ______________________________________ 3028917 Rhodes Well Completion Apparatus 3603401 Nelson et al Tubing Hanger Method and Apparatus 4154302 Cugini Cable Feed-Through Method and Apparatus For Well Head Constructions 42841 42 Kirkland Method and Apparatus For Remote Installation and Servicing Of Underwater Well Apparatus 4289199 McGee Wellhead Sidewall Electrical Penetrator 4600054 Miller et al Tubing Hanger Assembly 4651 831 Bangh Subsea Tubing Hanger With Muitiple Vertical Bores And Concentric Seals 4804045 Reed Oil and Gas Wells Diversionary Spool Assembly 5462119 de Souza et al Tubing Hanging Set For A Submarine Oil-Well, Running Tool For Its Placing and Handling Method 5560435 Sharp Method and Apparatus For Drilling Multiple Offshore Wells From Within A Single Conductor String ______________________________________